The present invention relates to a control unit including a microcomputer and a programmable nonvolatile memory and, more particularly, to a motor vehicle control unit including a microcomputer and programmable nonvolatile memory.
A control unit and a device for programming it are already known from EP 0 266 704 A2. In this case an external programming unit is provided for programming the nonvolatile memory of the control unit. The external programming unit is connected to the control unit via a serial transmission line. The data to be programmed are transmitted to the control unit via this serial transmission line. The microcontroller of the control unit receives the data and then programs them into the nonvolatile memory to be programmed. To this end, the necessary programming voltage is fed to the control unit via a separate connection between the programming unit and control unit. Therefore, there is a separate input pin provided at the control unit, to which input pin the programming voltage can be applied from the outside.
It is also known to generate the programming voltage internally in the control unit. The programming process is initiated using control instructions which are transmitted to the control unit via the serial transmission line. It is disadvantageous here that as a result of electromagnetic interference the program sequence of the control unit may be arbitrarily altered so that it is not ensured that the programming of the nonvolatile memory cannot be initiated wrongly.